There are different types of antivirus software, and each has its own advantages and disadvantages. Some antivirus software is free, while others have to be paid for. Some antivirus software only scans for viruses manually, while others do it automatically. Antivirus software is important because it helps to protect your computer from viruses.
Avast free antivirus
Scans files and Wi-Fi a computer connected to for security weaknesses. Does not include firewall and scanning internet browsing.
As per av-comparatives Avast detects 100% known viruses.
Kaspersky Security Cloud Free
'Protects against viruses' as per the description on the top vendor's website. Does not have a firewall or anything else. Android and iOS. As per av-comparatives Avast detects 99.2% of known viruses.
AVG AntiVirus FREE
Scans files on the computer as well as emails and links while you browse the internet. But it does not have a firewall and local WiFi scanning. Reportedly detects 100% known viruses.
Avira free security
This German free antivirus has a bunch of features on top of regular antivirus and internet browsing scanning. That includes generating secure passwords, blocking browser tracking and advertisements etc. As usual for all free antiviruses, it does not have a firewall. Although it detects only 98.9% of known viruses.
Bitdefender Antivirus Free
Scans computer and browsing the internet. No firewall. BD antiviruses detect only 99.7% of known viruses as per the av-comparatives chart.
Free antivirus tools
Antivirus Tools scan for viruses manually. They are good to detect and clean from viruses but they are not monitoring user activity continuously. You have to run them manually and click 'Scan' to look for viruses. Many free antivirus tools come as a bundle for other free downloadable products such as PDF reader or internet browsers. That may mislead you to believe that you have installed an antivirus. Examples are Trend Micro and Mcafee free antivirus scanners. Trend Micro called it HouseCall. Although they do have a free antivirus for mobile phones called Trend Micro Mobile Security for Android and iPhone. Mcafee also has free mobile antivirus with interesting features such as Contacts backup.
Free trial antiviruses
Almost every other vendor offers 30 days trials of their paid products. But do not forget to either pay or remove them after the trial period. Outdated trials do not protect 100% anymore and may cause trouble like slow down computers and interfere with another antivirus. You should have only one antivirus on a device. And of course, do not forget that Windows 10 comes with a built-in free antivirus Microsoft Defender.